Computer Science Previous Year Questions (page 45)

Explanation

In register indirect mode the chosen register holds the memory address of the operand, not the operand itself.

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VLINK sets the colour of visited links (those already clicked). LINK is for unvisited links and ALINK for the active link while it is being clicked.

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An assembler translates assembly mnemonics into machine code, and because assembly instructions map to a specific processor's instruction set, the program is machine dependent. Both are true.

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One-address instructions use an implied accumulator (AC) for all data manipulation, e.g. ADD X means AC = AC + M[X].

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Under the DPDP Act, 2023, a "child" is a person who has not completed eighteen years. Digital personal data is data in digital form, so B is wrong.

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Repositioning within a file (file seek) only changes the current-file-position pointer, so it needs no actual I/O.

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The Instruction Register (IR) holds the instruction currently being decoded and executed, for use by the control unit.

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Dictionary values may repeat, but keys must be unique; assigning to an existing key overwrites its value.

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The dispatcher gives control of the CPU to the process chosen by the short-term scheduler, doing the context switch and jump to user mode.

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A dot matrix printer strikes pins against an inked ribbon, so it is an impact printer. Inkjet, laser and thermal printers are non-impact.

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A point-to-point connection gives a dedicated link between exactly two devices. A shared, timeshared link describes a multipoint connection, so only I is correct.

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In DMA burst transfer, a block of several memory words is sent in one continuous burst while the DMA controller holds the bus. Cycle stealing transfers one word at a time.

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First Normal Form requires atomic attribute values, so it disallows nested relations or relations as attribute values within tuples.

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The HR tag supports SIZE, WIDTH, ALIGN and NOSHADE. There is no SHADE attribute.

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Copyright gives the creator legal rights over their original work, enabling them to earn recognition or financial benefit from its use.

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Much e-waste from developed countries is shipped to developing countries such as India, where metals like copper, iron, silicon, nickel and gold are recovered in recycling.

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A pandas DataFrame is a two-dimensional labelled data structure whose columns can hold different data types, like a table.

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A semaphore is accessed, apart from initialisation, only through the atomic operations wait() (P) and signal() (V).

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Security is a major challenge in IoT adoption, because many connected devices with weak protection can be hacked or leak data.

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The head element is a container for tags giving information about the page, such as title, meta, link and style. The body holds visible content.

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Discarded, irreparable computers and electronic goods are called electronic waste (e-waste).

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A pandas Series is a one-dimensional labelled array that can hold any data type. A DataFrame is two-dimensional.

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The E-Waste (Management) Rules 2016 cover IT and telecom equipment and consumer electrical and electronics, and also include compact fluorescent lamps (CFL) and other mercury-containing lamps. So both apply.

Explanation

An HTML comment starts with <!-- and ends with -->, as in option D.

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An ImportError (here ModuleNotFoundError) means Python could not find the pandas module among installed libraries, so only III is correct.

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set_index() takes a column name or list of column names and returns a new DataFrame indexed by those columns.

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Python identifiers may contain letters, digits and underscores, so _ is allowed. They cannot start with a digit, cannot be keywords, and have no length limit.

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XML element names must not start with "xml" (in any case), cannot start with a number or contain spaces, but can contain letters, digits and characters like hyphen and underscore.

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Intellectual property rights are given to the creator or inventor, giving legal protection over their creation or invention.

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In Python, # starts a single-line comment; everything after it on that line is ignored.

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pandas merge() joins DataFrames on common columns, like SQL joins, so tables can be combined as in a database.

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IPR such as patents and copyrights are granted for a certain, fixed period of time, after which the work enters the public domain.

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Exposure variability depends mainly on the type of e-waste, since different devices contain different toxic substances such as lead, mercury and cadmium.

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The <BR> tag inserts a line break. <B> makes text bold; <BL> and <L> are not standard tags.

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CEILING returns the smallest integer greater than or equal to the value, e.g. CEILING(4.2) = 5. FLOOR returns the largest integer less than or equal to it.

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LRU is a stack algorithm and never suffers from Belady's anomaly. FIFO can give more page faults with more frames, so it does suffer from it.

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A string is a sequence of characters, which can include letters, digits and symbols, e.g. "Ab12#@".

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SELECT * retrieves all attributes (columns) of the selected tuples.

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UTF-8 is the most widely used Unicode encoding; it uses 1 to 4 bytes per character and is ASCII-compatible. UTF-17, 61 and 35 do not exist.

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Files like .txt, .py and .csv store plain human-readable characters, so they are text files.

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The gate shown has an extra curved line at the input side of the OR shape, which is the symbol for the Exclusive-OR (XOR) gate.

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The semantic analyzer checks meaning and gathers type information, storing it in the syntax tree or symbol table for intermediate code generation.

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Numbers with a decimal point (like 3.14) are fractional/floating point numbers, stored as float in Python. Integers have no decimal part.

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The set difference R − S contains tuples that are in R but not in S. ∩ gives common tuples, ∪ all tuples, × the Cartesian product.

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SQL aggregate functions include COUNT, SUM, AVG, MAX and MIN. Cross product is a relational join operation, not an aggregate.

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Unicode assigns a unique number (code point) to every character of every written language, regardless of platform, device or program.

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ASCII uses 7 bits (128 characters), enough mainly for English, so it can handle only one, or at most two, languages.

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Per Elmasri-Navathe, an entity type defines a collection of entities that have the same attributes; the actual set of entities at a moment is the entity set.

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Python uses # for comments, which make code more readable and are ignored by the interpreter.

Explanation

During a context switch the kernel saves the old process state in its PCB and loads the new one's. This switching time is pure overhead, since no useful work is done. Both are correct.